This database derived from the testing of approximately 1000 chemicals for mutagenicity in Salmonella typhimurium is being analyzed. These chemicals were tested in 4 Salmonella strains without metabolic activation, and with 2 different S-9 preparations, for a total of 12 strain/activation combinations, and some of the chemicals were tested in more than one laboratory. We therefore have the opportunity to analyze numerous parameters. Analysis of the effectiveness of different testing strategies for mutagen detection has shown that TA100, alone, is the most effective strain. A number of 2- and 3-stage testing schemes have been proposed which are more efficient and cost-effective than the use of all tester strain/activation combinations simultaneously. Additional analyses of the data-base are planned or in progress.